Tracking of air mass movement

ABSTRACT

The movement of an air mass is monitored by releasing a tracer entity at aiven location, collecting a sample of air at a different location and analyzing the collected sample of air for the presence of the tracer entity by using Bacillus thurengiensis as the tracer entity and by analyzing for the presence of the bacterium by effecting a culture in a medium capable of supporting bacterial growth and preferably containing citrate as the sole source of assimilable carbon.

BACKGROUND OF THE INVENTION

It is frequently desirable to monitor or track the movement of a mass ofair. For example, air mass movement is important in weather forecastingwhere it is often monitored by examining changes in ambient atmosphericpressure. Studies of the phenomenon of acid rain, industrial plantemissions or of chemical or biological weapon attacks also need physicalverification of the expected movement of the air masses involved inorder to ascertain whether various predictions or assumptions are valid.

Theoretical discussions of air mass movement can be found in the "AirPollution Handbook", McGill et al. (McGraw-Hill Book Co., 1956) Section4-54 at pp. 54-59; Sutton, "Atmospheric Turbulence" (John Wiley & Sons,1949); and Sutton, "Micrometeorology" (McGraw-Hill Book Co., 1953).

One of the present means of monitoring the movement of an air mass hasbeen by releasing fluorescent particles of zinc cadmium sulfide or zincsulfide into the air and sometimes by the release of a radioactiveparticle. A sample of the air mass is collected downwind. The presenceof the fluorescent particles or radioactive particles in the collectedsample is thereafter determined using suitable equipment such as, forexample, a fluorometer or a radioactive counter. However, cadmium isknown to be toxic and therefore its use is undesirable. It is alsoundesirable to release sulfides into the atmosphere or to releaseradioactive materials into the atmosphere. Accordingly, a need existsfor a safe and reliable method of tracing air mass movement.

It is accordingly the object of this invention to provide a method forthe monitoring of the movement of an air mass without the release oftoxic, radioactive or other undesirable material into the atmosphere.This and other objects of the invention will become apparent to those ofordinary skill in this art from the following detailed disclosure.

SUMMARY OF THE INVENTION

This invention relates to a method of monitoring the movement of an airmass and more particularly to the monitoring of the movement of an airmass by releasing a tracer entity at a given location, collecting asample of the air at a different location and analyzing the collectedsample of air for the presence of the tracer entity in which the tracerentity is Bacillus thurengiensis and the analysis is effected byculturing the collected sample on a medium capable of supportingbacterium growth. Preferably, the growth medium contains citrate as thesole source of assimilable carbon.

DESCRIPTION OF THE INVENTION

In accordance with the present invention, the movement of an air mass ismonitored by introducing a quantity of Bacillus thurengiensis into theatmosphere at one or more given locations and positioning samplingequipment one or more points of interest to collect all of the materialpresent in the ambient air. The collection equipment is usually placeddownwind of the release point, but may also be in other locations todetermine if there are any unexplained or unexpected movement of theair. Frequently, a plurality of collection points forming a more or lessregular grid pattern is established in order to achieve a more completeplot of the air's movement.

Bacillus thurengiensis is a widely used entomopathogen. It wasoriginally isolated from natural epizootics in susceptible Lepidopteriain Japan and Germany. Various formulations of Bacillus thurengiensishave been commercially available for use in agriculture since themid-1950s. A potent strain was introduced commercially in the 1970sunder the trademark DIPEL. In 1977, a further strain named Bacillusthurengiensis var israelensis was isolated in a stagnant pool in a riverbed in the Negev Desert and later designated as Bacillus thurengiensis,Serotype H-14. The World Health Organization has developed a standardpreparation of Serotype H-14 under the designation IPS-78.

Bacillus thurengiensis is a spore forming, very hardy bacterium which issafe for warmblooded animals including humans. As a practical matter,the bacterium is an insecticide only for caterpillars and mosquitoes andit is not persistant in the environment. These characteristics make theBacillus thurengiensis particularly useful in the present invention.

In order to trace the movement of an air mass, the bacterium is releasedinto the atmosphere as a cloud of wet or dry particles generally, butnot necessarily, in the 2-5 micron range. The bacterium can be releasedinto the atmosphere in the same manner as it is used as a selectiveinsecticide. For example, one can use a land-based atomizer or aerialspraying can be employed. The quantity released is not critical andtheoretically a single spore is all that is necessary. More practically,a quantity of about 110-230 grams of Bacillus thurengiensis powder(having a potency of 1000 to 2000 Aedes Aegypti International ToxicUnits) can be employed per release location but greater but lesseramounts can also be employed, if desired.

Any conventional method of collecting airborne bacteria can be employedat the collection point or points in the process of this invention. Thebasic methods which can be employed include impingement in liquids,impaction on solid surfaces, filtration, sedimentation, centrifugation,electrostatic precipitation and thermal precipitation. A wide variety ofinstruments are available for practicing these collection methods. Anexcellent survey of these sampling methods and the equipment employedtherein can be found in "Sampling Microbiological Aerosols", PublicHealth Monograph No. 60, issued by the Public Health Service of the U.S.Department of Health, Education and Welfare (Public Health ServicePublication No. 686).

The airborne detrius, i.e., the material found in the ambient air,various pollens, fungi, spores, soil bacteria, soil particles, soot andassorted man-made particles, in the collected sample or samples iscultured, i.e., the collected fraction of particulates in the atmosphereare combined with a suitable culture medium which can support the growthof the bacterium.

Beyond the known safety to humans, plants, domestic animals and almostall lower life forms, and the established methods of introduction intothe atmosphere, the use of Bacillus thurengiensis is particularlyadvantageous for two reasons. First, the microbe grows at roomtemperature so that no complex equipment is needed. Second, thebacterium is unusual in that it can metabolize the citrate ion as asource of carbon while almost all other known spore forming bacteria arenot so capable. Further, the inclusion of citrate in an acidic statealso inhibits the growth of other microbes. These characteristicssimplify the analysis procedure and provide for greater accuracy sincethe growth of other spore forming bacteria need not be distinguished inthe medium. Accordingly, while the culture can be effected in any mediumcapable of supporting growth, it is preferably carried out in a mediumcontaining citrate as the sole source of assimilable carbon. Any of theknown citrate media which do not contain another assimilable carbonsource can be employed.

A particular advantageous medium is the Koser Citrate Medium which indehydrated form contains 1.5 grams of sodium ammonium phosphate, 1 gramof mono-potassium phosphate, 0.2 gram magnesium sulfate and 3 grams ofsodium citrate. In this medium, the ammonium salt serves as the solesource of nitrogen and the sodium citrate as the sole source of carbon.To rehydrate this medium, 5.7 grams are dissolved in 100 ml of distilledwater. Another typical citrate medium is Simmons Citrate Agar whichcontains 0.2 gram magnesium sulfate, 1 gram of monoammonium phosphate, 1gram dipotassium phosphate, 2 grams sodium citrate, 5 grams sodiumchloride, 15 grams agar and 0.08 gram bromthymol blue.

A typical culture medium which can be used in the present invention willcontain 5.7 grams per liter Koser Citrate Medium, 10 grams per litercaseine enzymatic digest, 0.03 gram per liter MnSO₄, 0.02 grams perliter FeSO₄, 0.002 gram per liter thiamine hydrochloride and 15 gramsper liter agar. Since only one Bacillus thurengiensis spore is needed inorder to detect its presence, the test of the present invention is verysensitive. The single spore grows and replicates itself many times.

An example of one use of the present invention concerns an evaluation ofthe accusation that fluoride emissions from an aluminum plant waskilling cattle located at a distance of about 10 miles from theproduction plant. A solution of Bacillus thurengiensis spores is sprayedinto the atmosphere at the plant site under various weather conditionsand collection devices are installed at the location where the cattledeaths occurred. The collected material is then cultured in theselective medium to determine the presence or absence of the bacterium.Since both the fluoride emissions and the bacterium will be carried awayfrom the aluminum plant by the same air mass, the results of theculturing provides an indication of whether the fluoride may havetraveled from the plant to the place of the cattle fatalities.

Various changes and modifications can be made in the method of thisinvention without departing from the spirit and scope thereof. Thevarious embodiments which have been disclosed herein were for thepurpose of further illustrating the present invention and were notintended to limit it.

What is claimed is:
 1. In a method of monitoring the movement of an airmass comprising releasing a tracer entity into the atmosphere at a givenlocation, collecting a sample of the ambient air at a different locationand analyzing the sample of the collected air for the presence of thetracer entity, the improvement which comprises employing Bacillusthurengiensis as the tracer entity and conducting the analysis byperforming a culture on the collected sample in a medium capable ofsupporting Bacillus thurengiensis growth.
 2. The method of claim 1 inwhich samples of air are collected at a plurality of locations.
 3. Themethod of claim 2 in which said medium contains citrate as the solesource of assimilable carbon.
 4. The method of claim 3 wherein theculture medium contains Koser Citrate Medium.
 5. The method of claim 1in which said medium contains citrate as the sole source of assimilablecarbon.